Process of treating precious-metal-bearing materials.



UNITED STATES PATENT @FEIQE.

PROCESS OF TREATING PREClOUS-METAL-BEARING MATERIALS.

Specification of Letters Patent.

Patented Oct. 10, 1905.

Application filed December 28, 1904. Serial No. 238,668.

To all whom, it may concern:

Beitknown that I, CHARLES IN. MERRILL, a citizen of the United States,and a resident of Lead, in the county of Lawrence, State of SouthDakota, have invented certain new and useful Improvements in Processesof Treating Precious-Metal-Bearing Materials, of which the following isa specification.

My invention relates to an improvement in the art of treatingprecious-metal-bearing material, particularly those ores or tailingswhich contain reducing salts or minerals with cyanogen-bearingsolutions; and it consists in subjecting the particles of saidprecious-metalbearing material to the action of an oxidizing agent afterthe removal of the liquid when there present from the interstitialspaces and before bringing the cyanogen-bearing solution in contact withsaid precious-metal-bearing material.

In the usual method of treating ores, tailings, or likeprecious-metal-bearing materials with alkaline cyanid solutions it isoften found, by reason of the presence in the material which is beingtreated of reducing salts or minerals or for other reasons, that thedissolving action of cyanogen-bearing solutions on the precious metalsis reduced to nothing or much diminished, because this reducingmaterial, or compounds yielding reducing material, which is frequentlypresent in large quanties, abstracts the dissolved oxygen from thesolution, which dissolved oxygen is essential to the dissolution of theprecious-metal contents. Furthermore, certain reducing materials, suchas ferrous compounds, have a greater affinity for potassium cyanid thanthe corresponding higher chemical combinations, such as ferriccompounds, and consequently by first bringing lower compounds to ahigher state of oxidation by the introduction of some kind of oxidizingagent, such as atmospheric air, a material saving is effected in theconsumption of the cyanogen, which is in itself an expensive reagent. Inpractice it has been found difficult, tedious, and often impossible tooxidize all or part of the reducing material when the interstitialspaces of the precious-metal-bearing material are filled with liquid orwith a quiescent gas not under pressure. When, however, crushedmetalbearing material is collected in a container, the liquid when therepresent removed from the interstitial spaces, and atmospheric air orother oxidizing agent is applied thereto under pressure, the effect ofthe oxidizing agent upon the reducing substances is very much greater,for the reason that in this manner an envelop of oxidizing agent underpressure is formed around the particles of solid matter and the saidcontact or envelop is maintained and renewed when necessary until partor all of the reducing material has been oxidized, after which the airor other oxidizing agent is then displaced and the metallurgicaltreatment continued.

As is well known, all methods of crushing ore are divided, generallyspeaking, into what is known as dry crushing and wet crushing the latternecessitating the presence of liquid in the material. The effect of theliquid being present with the crushed ore is merely an incident to theoperation and not essential, and hence in my process in the latter caseprior to eflecting oxidation preliminary to the contact of a cyanidsolution the liquid is removed from the interstitial spaces. This may beefiected by draining the containers in any convenient manner, afterwhich the interstitial spaces are filled with the oxidizing agent, andthe contact thus formed be tween the finely-divided metal-bearingmaterial and the oxidizing agent is maintained until part or all of thereducing material has been oxidized. In the event of the crushedmetal-bearing material having been charged in the container by what isknown as the dry methodnamely, one which does not leave the interstitialspaces filled with the liquid the same process is pursued, except thatin this alternative it is not necessary to remove liquid from theinterstitial spaces for the purposes of attaining the first oxidation.

The process may be conducted in any form of a container to which theoxidizing agent may be applied under pressure after the removal of anyliquid when there present from the interstitial spaces.

I claim as my invention 1. The improvement in treatingpreciousmetal-bearing material with cyanogen-bearing solutions aftercrushing, consisting in removing the liquid when there present from theinterstitial spaces of the crushed material, then applying an oxidizingagent under pressure to said material, and subsequently bringing thecyanogen-bearing solution in contact with said material.

2. The improvement in treating preciousmetal-bearing materials withcyanogen-bearing solutions after crushing, consisting in removing theliquid when there present from the interstitial spaces of the crushedmaterial, then applying atmospheric air under pressure to said material,and subsequently bringing the cyanogen-bearing solution in contact withsaid material.

3. The improvement in treating preciousmetal-bearing materials withcyanogen-bearing solutions after crushing, consisting in removing anyliquid when there present from the interstitial spaces of the crushedmaterial, then applying atmospheric air under pressure to said material,and subsequently bringing the cyanogen-bearing solution in contact withsaid material, in one and the same container.

a. The improvements in treating preciousmetal-bearing materialcontaining reducing agents, with cyanogen-bearing solutions consistingin first collecting said material in a con- CHARLES W. MERRILL.Witnesses:

WM. FRACKELTON, GEO. D. FOGLESONG.

